1. Field of the Invention
The invention relates to a circuit arrangement for supplying a single or multi-phase inductive load from a d-c voltage source and, in particular, a circuit arrangement of the type comprising a self-commutating inverter having valve branches that can be fired and extinguished and d-c voltage inputs to which are connected electronic switching members.
2. Description of the Prior Art
In inverters with forced commutation and phase sequence quenching, quenching capacitors whose charge is reversed by the load current during each commutation cycle are arranged between the valve branches. If an inductive load and in particular an electric machine, is connected to the inverter, the voltage at the quenching capacitors can increase during the commutation process beyond the voltage induced by the load. However, the voltages at the quenching capacitors must not become too high or the voltage stress on the controlled valves of the inverter as well as the dielectric stress on the insulation of the load will become excessive.
The size of the quenching capacitors in the aforesaid inverter arrangements must, therefore, be chosen to best satisfy two countervailing requirements. On the one hand, the aforesaid need to limit the voltage on the quenching capacitors requires quenching capacitors with relatively large capacities. On the other hand, the need to maintain a sufficiently long protection time so as to be able to reliably extinguish the valves of the inverter dictates the need for quenching capacitors having relatively small capacities.
It is an object of the present invention to provide a circuit arrangement for supplying an inductive load in which an inverter with forced commutation is employed and in which the quenching capacitors between the individual valve branches of the inverter can be as small as possible and can be designed so as to only satisfy the protection time requirement of the controlled valves.